Novel photographic color processes and products



H. G. ROGERS 3,015,561

NOVEL PHOTOGRAPHIC COLOR PROCESSES AND PRODUCTS Jan. 2, 1962 Filed March15, 1957 Layer Con'l'qining Color-Providing Subs'l'ance Layer ofReducible Polymer ho'l'osensi'live Emulsion FIG. l

Supporl' 32 Phol'osensilive Emulsion 34 7 {Processing Composi'l'ionConl'oining Color-Providing Subs-lance \Lqyer of Reducible Polymer FIG.2

Image Receiving Layer Con'l'oining Color-Providing Subs'l'oncePho-l'osensi'l'ive Emulsion Composi'l'ion Image Receiving Layer FIG. '3PP 70 Suppor'l 72 -Pho-l'osensil'ive Emulsion 76 Processing Composil'ion78 k Layer of Reclucible Polymer V EN TOR.

ZM M m e/ m o is, I

Suppori United States Patent ice 3,015,561 Patented Jan. 2, 1962 wareFiled Mar. 15, 1957, Ser. No. 646,384 5 Claims. (CI. 96-29) Thisinvention relates to the art of photography and, more particularly, tonovel processes for the formation of color images and to photographicproducts for use with such processes.

It has previously been proposed, as for example in US. Patent No.2,647,049, issued to Edwin H. Land on July 28, 1953, to form colorphotographs by a diffusiontransfer reversal process. In such a process,a photosensitive layer containing a latent color record image isprocessed to develop said latent image and to form a positive colorrecord in an image-receiving element.

The present invention is concerned with improvements in the formation ofcolor images by diffusion-transfer reversal processes and particularlywith providing novel processes utilizing, as the means of controllingthe diffusibility of a color-providing substance, a substance reducibleby unreacted developing agent.

A primary object'of this invention, therefore, is to provide novel colorprocesses wherein the formation of an imagewise distribution ofcolor-providing substance is elfected by the reducing action ofunoxidized or unexhausted developing agent on a reducible substance, andmore particularly, a reducible polymeric substance.

A further object of this invention is to provide improveddiffusion-transfer reversal processes for the forma' tion of colorimages, preferably positive color images, wherein the creation of avisible image is effected by the action of unexhausted developing agenton a reducible polymeric substance.

Another object of this invention is to provide novel diffusion-transferreversal processes for the formation of color images, wherein thecolor-providing substance is nondifiusible until a reducible substanceis acted upon by unexhausted developing agent, and wherein saidcolorproviding substance is an organic compound.

Another object of this invention is to provide novel dif fusion-transferreversal processes for the formation of color images wherein thecolor-providing substance is a complete dye.

These and further objects of the invention will in part be obvious andwill in part appear hereinafter.

The invention accordingly comprises the processes involving the severalsteps and the relation and order of one or more of such steps withrespect to each of the others, and the products possessing the features,properties and the relation of elements which are exemplified in thefollowing detailed disclosure, and the scope of the application of whichwill be indicated in the claims.

For a fuller understanding of the nature and objects of-the invention,reference should be had to the following detailed disclosure taken inconnection with the accompanying drawing wherein:

FIGURE 1 is a diagrammatic cross-sectional view of one embodiment of aphotosensitive element, suitable for use in the process of thisinvention, in association with an image-receiving element and arupturable container holding a liquid processing composition;

FIG. 2 is a diagrammatic cross-sectional view of a further embodiment ofa photosensitive element, imagereceiving element and rupturablecontainer suitable for use in the process of this invention;

FIG. 3 is a diagrammatic cross-sectional view of another embodiment of aphotosensitive element, imagereceiving element and rupturable containerin accordance with this invention; and

FIG. 4 is a diagrammatic cross-sectional view of still anotherembodiment of a photosensitive element, imagereceiving element andrupturable container suitable for use in one embodiment of thisinvention.

In diffusion-transfer reversal processes of the type hereincontemplated, an exposed photosensitive silver halide emulsion layercontaining a latent image is processed by a liquid processingcomposition to obtain an imagewise distribution of ditfusiblecolor-providing substances. A positive color image may be obtained bythe transfer of at least part of such imagewise distribution ofdifiusible color-providing substances by imbibition from the developedphotosensitive layer to a superposed image-receiving material. Thedesired positive color image is revealed by separating or stripping theimage-receiving material from the developed photosensitive layer after asuitable imbibition period.

Diffusion-transfer reversal color processes hitherto proposed haveemployed various color-producing mechanisms, both for providing theimagewise distribution of diffusible color-providing substances in thedeveloped photosensitive layer and for imparting the desired posi-' tivecolor image to an image-receiving material. Thus, the previouslymentioned US. Patent No. 2,647,049 proposes to employ color couplers andcolor developers of a nature common in conventional color processes. Inutilizing such color couplers and color developers, the desiredimagewise distribution of color coupler and color developer is dependentupon the immobilization of at least the oxidized color developer in thephotosensitive layer as a result of the development of a latent image.In such processes, unreacted color developer and color coupler aretransferred to an image-receiving material and there reacted to producethe desired dye image It will be noted that such processes requireaseries of reactions to provide the ditfusible imagewise distribution and.to produce the desired dye image'utilizing the ditfusible utilize dyedevelopers, that is, complete dyes which have a silver halide developingfunction. Utilization of dye developers as contemplated therein has theadvantage of reducing the number of reactions necessary to provide thepositive dye image since the dye developer is a complete dye and nocoupling reactions are required in the photosensitive layer or to impartthe desired dye image to the image-receiving material.

It has also been proposed to employ complete dyes in diffusion-transferreversal color processes by utilizing an oxidation product of the silverhalide developer to immobilize the dye in exposed areas and thus providethe desired imagewise distribution of difiusible dye. Processes of thistype are disclosed and claimed'in my US. Patent No. 2,774,668, issuedDecember 18, 1956.

' It Will, therefore, be seen that'ditfusion-transfer reversal ponentsmust be trapped, that is, immobilized, in the exposed portions of thephotosensitive layer.

The novel dillusion-transfer reversal color processes of this inventionmay be readily distinguished from such previously proposed processes bythe fact that a mobilizing mechanism is employed to provide the desiredimagewise distribution of dilfusible color-providing substances. Thus,the processes of this invention control the availability for transfer ofcolor-providing substances associated with unexposed areas of thephotosensitive layer by the reaction of unreacted or unexhausted silverhalide developing agent upon a reducible substance, and moreparticularly, a reducible polymeric substance.

By way of recapitulation, the novel processes of this invention dependupon the action of unexhausted developing agent to controltheavailability for transfer of a color-providing substance. Thus, thecolor-providing substance is rendered transferable imagewise by thereducing action of unexhausted developing agent on a reducible polymericsubstance.

It will, therefore, be readily apparent that the noveldiflusion-transfer reversal color processes of this invention providenovel methods of creating the desired imagewise distribution of mobilecolor-providing substances.

The expression color-providing substances as used herein is intended toinclude all types of reagents which may be utilized to produce a colorimage and which are capable of being rendered soluble in a processingliquid. Such reagents are organic in nature and may initially possess achromophoric system imparting the desired color in the state in whichthey are diffusible, or the reagents may undergo reaction after transferto form such a chromophoric system, as by oxidation and/ or coupling. Ina preferred embodiment the color-providing substances are complete dyes.It is also contemplated to use a color-providing substance, which in itsditiusible form is a leuco dye but which is oxidized after imbibition toprovide the desired positive dye image. The nature of these and othercolor-providing. substances will be referred to in more detailhereinafter. V

The oxidation potential of the reducible polymeric substance should beintermediate between that of exposed silver halide and unexposed silverhalide, whereas the reduction potential of the silver halide developingagent should be such that in exposed areas it will develop exposedsilverhalide substantially to the exclusion of reaction With the reduciblepolymeric substance and in unexposed areas will react with the reduciblepolymeric substance substantially to the exclusion of unexposed silverhalide.

composition is applied to the photosensitive element in a.

uniform layer as the photosensitive element is brought into superposedrelationship with an image-receiving element.

. It is also within the scope of; this invention to apply the liquidprocessing composition prior to exposure in accordance with thedisclosure in the copending application of Edwin H. Land, Serial No.498,672, filed April 1, 1955. The liquid processing compositionpermeates the emulsion to provide a substantially uniform distributionof the silver halide developing agent therein. The silver halidedeveloping agent may be initially contained in the liquid processingcomposition or it may be initially disposed in the photosensitiveelement.

As the latent image is developed by the silver halide developing agent,an imagewise distribution of unreacted or unexhausted silver halidedeveloping agent is formed. This imagewise distribution of unexhaustedsilver halide developing agent is formed as a function of thepoint-topoint degree of exposure creating the latent image. The amountof unexhausted developing agent is thus inversely related to thequantity of silver halide developed, and the quantity of color-providingsubstance available for transfer will vary directly with the amount ofunexhausted developing agent.

The above-mentioned imagewise distribution of unexhausted silver halidedeveloping agent present in the unexposed areas of the photosensitiveelement reduces a reducible polymeric substance so located in thislamination as to normally prevent the color-providing substance fromhaving access to the image-receiving material. The reduced form of thereducible polymeric substance is permeable to the liquid processingcomposition. As a result of the change in permeability of such reducedportions of the reducible polymeric substance, an imagewise distributionof difiusible color-providing substance is created. At least part ofthis imagewise distribution of mobile color-providing substance is transferred, by irnbibition, to a superposed image-receiving layer orelement. Under certain circumstances, the layer of liquid processingcomposition may be utilized as the image-receiving material. The latterelement receives a depthwise diffusion from the'photosensitive elementof mobile color-providing substance, without appreciably disturbing theimagewise distribution thereof, to provide a reversed or positive imageof the developed image. The

desired positive image is revealed by stripping the imagereceivingmaterial from the photosensitive element at the end of the imbibitionperiod.

By the expression immobile color-providing substance, as used herein, ismeant a color-providing-substance which is incapable of transferring to,an image-receiving material because of a reducible polymeric substance,at least during the period of imbibition. The term mobile colorprovidingsubstance refers to a color-providing substance rendered transferable asthe result of the reducing action of unexhausted silver halidedeveloping agent on a reducible polymeric substance.

The reducible polymeric substances employed in the processes of thisinvention are substantially impermeable in the unreduced state to theprocessing composition, at least during the imbibition period. Reductionby unexhausted developing agent renders the reduced portions ofpolymeric substance permeable to the processing composition. Thus, theunreduced polymeric substance is substantially non-swellable by alkali,and the reduced portions thereof are swellable by alkali. The polymersshould be free of excessive water-solubilizing groups, such as sulfonicacid groups, so that it will not be waterswellable in the unreducedstate. i

The desired permeability characteristics of the reducible polymericsubstance result from the fact that the polymer is so constituted thatits permeability is dependent upon the state of the reactive groupspresent. These reactive groups are so chosen as to be insoluble inalkali until reduced, in accordance with well-known chemical principlesthat the reduced forms are more soluble. The permeability, for example,may result from the ability of the reactive groups to form alkali metalsalts in the r duced form but not in the oxidized form.

As examples of reducible polymeric substances, mention may be made ofpolymers containing reducible functional groupings, for example,indophenol or quinone groups. The reducible polymers preferably shouldbe soluble in organic solvents to facilitate their use in preparing thephotosensitive products.

Polymers containing indophenol groups may be prepared by oxidativecoupling of p-phenylene diamine type compounds with so-called polymericcolor couplers. Polymeric color couplers are well-known in thephotographic art and are polymers, for example, polyvinyl alcohol,containing substituents capable of coupling with the oxidation productof color developers. Such substituents may comprise phenolic ornaphtholic groups having a coupling position available para to thehydroxyl group, and the term indophenol is intended to refer to thegrouping which results from such coupling. Thus, one may react polyvinylalcohol with salicylaldehyde in an acetal synthesis to obtain thepolymeric coupler polyvinyl salicylal.

Another suitable type of reducible polymer comprises polymers havingreducible metal complex groups. As examples of suitable polymers,mention may be made of polymers having ,S-ketone or ,B-ketonitrilesubstituents capable of forming reducible manganic complexes.

Additional reducible polymers comprise polymers containing reducibledisulfide linkages or heavy metal salts, for example silver salts, ofpolymers containing mercapto groupings.

Where the impermeable characteristics make operations such as coatingdifficult, it is contemplated to introduce the polymeric substance in acoatable state and convert it to the impermeable state in situ. Thus,where the reducible polymer is to be used in the form of a coating, itis contemplated to first apply a coating of the permeable form or of anintermediate and thereafter convert it to the reducible, impermeableform by suitable treatment. Thus a coating of a polymeric coupler, e.g.,polyvinyl salicylal, may be applied and then treated under oxidizingconditions with a para-phenylene diamine type compound to form theimpermeable indophenol polymer. The reducible polymeric substance may becolored or colorless, so long as the color thereof does not interferewith effective use thereof. In certain instances, it may be desirable toemploy a colored reducible polymer to obtain an image in terms of twocolors, that is, an image in one color on a background of another color.Where the reducible polymeric substance is to be contained in thephotosensitive element and is itself colored, it is preferably employedbehind the emulsion to avoid undesirable light absorption. The reduciblepolymeric substance is preferably colorless if it is to be used as acomponent of the image-receiving element and is to remain there. Whereit is desired to utilize colored reducible polymeric substances in theform of particles in the emulsion, undesired light absorption may bereduced by using particles of such size as to have low covering power.In multilayer embodiments, only the reducible polymeric substancesassociated with the top two emulsions need be in the form of particlesfor this purpose, and the reducible polymeric substance associated withthe innermost emulsion layer may be used as a layer behind saidinnermost emulsion. Sould the color-providing substance present in suchparticles be itself colored, it may be present in the form of polarizingcrystals in accordance with the disclosure of the copending applicationof Edwin H. Land, Serial No. 607,820, filed September 4, 1956, and alayer of reducible polymer provided around such crystals. In allinstances where particles are employed, it is desirable that lightstriking the emulsion not be scattered in the course of transmission.Thus, the particles should approximately match the index of refractionof the medium of the photosensitive emulsion, e.g. gelatin.

Suitable color-providing substances for use in the processes of thisinvention include all types of complete dyes as well as dyeintermediates, such as color couplers. The color-providing substancesare preferably water-soluble, or at least alkali-soluble. Where thecolor-providing substance is a color coupler,-coupling of the colorcoupler rendered transferable by the action of unexhausted developingagent may be efiected, after transfer to the image-receiving material,with a substance, e.g., a diazonium salt or an oxidized color developer,initially present therein of introduced after the transfer is completed.When the developing agent utilizedto reduce the reducible polymericsubstance has an oxidation product capable of coupling with the couplerto form a diffusible dye, the desired image may be formed in thismanner. The color-providing. substances are preferably photographicallyunreactive and thus do not interfere with processing. lg

In certain instances, as where a color-providing substance is to beincorporated in the reducible polymeric substance, and especially inparticles thereof, the colorproviding substance should bewater-insoluble but soluble in alkali and organic solvents. Suchsolubility characteristics facilitate the use of the color-providingsubstance in the reducible polymeric substance.

The use of color-providing substances which are watersoluble isadvantageous in the preparation of additional transfer prints bysuperposing the developed and stripped photosensitive element withadditional image-receiving layers in the presence of a solubilizingcomposition. In such an embodiment, it may be desirable to neutralizethe developed negative to prevent aerial oxidation of the reducedportions of the reducible polymeric substance. This would preclude theuse in this embodiment of colorproviding substances requiring thepresence of alkali for diifusibility. The color-providing substance maythen be transferred using a non-alkaline solvent. including organicsolvents.

As previously indicated, the reducible polymeric substance employed isone which has an oxidation potential intermediate that of exposed silverhalide and unexposed silver halide and which exhibits a relatively largechange in permeability to the processing composition as between theinitial, oxidized condition and its reduced condition.

The silver halide developing agents which may be employed in conjunctionwith a reducible polymeric substance should exhibit a reductionpotential such that in exposed areas it will develop exposed silverhalide substantially to the exclusion of reaction with the reducible,.polymeric substance, and in unexposed areas it will react with thereducible polymeric substance, substantially to the exclusion ofunexposed silver halide. Preferably, the oxidation product of the silverhalide developer should be relatively insoluble to insure absence oftransfer thereof to the image-receiving material where it might causestain. Use of a silver halide developing agent having a relativelyhighly insoluble oxidation product also avoids the possibility of anequilibrium condition and insures completeness of reaction.

The silver halide developing agent is preferably employed in aconcentration such that it will becompletely reacted or exhausted inphotosensitive areas which have been completely exposed thus preventingstain in the highlights. The amount of exhausted developer is thus adirect function of the degree of exposure on a point-t0- point basis ofthe photosensitive emulsion and the amount of unexhausted developer isan inverse function of the amount of such exposure. The quantity ofalkali employed is preferably so limited as to be sufficiently exhaustedin exposed areas by the development reaction as to be incapable ofreleasing the colorproviding substance in said exposed areas.

As examples of suitable silver halide developing agents, mention may bemade of hydroquinone, toluhydroquinone, acetamidophenyl hydroquinone,p-anilinohydroquinone, naphthylazohydroquinone, Amidol (2,4-diamino-phenol hydrochloride), and Phenidone (l-phenyl-3-pyrazolidone).

Illustrative physical embodiments of the present invention, as shown inFIGS. 1 through 4, generally involve photosensitive elements which haveassociated therewith a liquid-carrying container, said container beingpositioned so that its liquid compositon can be released so as to permitthe permeation of the photosensitive emulsion by the liquid composition.A color-providing substance is present in the processing composition orin the photosensitive element. The liquid composition is preferably arupturable container viscous and includes at least a solvent for thesilver halide developing agent and also a solvent for the colorprovidingsubstance.

- The embodiment shown in FIG. 1 depicts a photosensitive elementwhichincludes a support layer 10 carrying a layer 12 containing acolor-providing substance. Between this layer and a layer 16 of aphotosensitive emulsion is a layer 14 of a reducible polymer. Arupturable container or pod 18 carrying a liquid processing composition,which composition includes a silver. halide developing agent and asolvent for the color-providing substance, is associated with thephotosensitive element and is adapted to release the processingcomposition for spreading between said photosensitive element and asuperposed image-receiving element comprising a support 22 carrying alayer 20 of a dyeabl'e, image-receiving material. In the course ofprocessing unexhausted developing agent present in unexposed areas ofthe emulsion reducesthe portions of the reducible polymer layer '14associated with such unexposed areas, and renders such portionspermeable to the processing composition. Permeation of the processingcomposition through such reduced portions of the-reducible polymer layer14 solubilizes the color-providing substance present in the layer 12behind the reducible polymer, and the thus-formed imagewise distributionof solubilized color-providing substance is transferred to the layer 20of image-receiving material.

FIG; 2 illustrates a photosensitive element comprising a support layer30 carrying a photosensitive emulsion layer 32. Associated with saidphotosensitive element is 34 containing a liquid processing composition,which composition includes a silver halide developing agent and acolor-providing substance. An image-receiving element comprises asupport 40, a layer 38 of image-receiving material and an outer layer 36of a reducible polymer. emulsion layer 32 results in an unexhausteddeveloping agent. The unexhausted developing agent reduces the reduciblepolymer rendering 'it permeable to the processing composition. Thecolor-providing substance present in the processing composition is thusfree to transfer imagewise to the image-receiving layer 33. Where thereducible polymer is colored or has an undesired color, it may beremoved by adhering to the photosensitive element upon stripping byproviding a suitable stripping layer between the layers ofimage-receiving material and reducible polymer.

A further embodiment of this invention is shown in FIG. 3 wherein aphotosensitive element includes a support layer 50 and a photosensitiveemulsion layer 54 containing particles 52 of a reducible polymerdispersed therein. The particles 52 contain a color-providing substance.Thus, particles 52 comprise a color-providing substance controlled by anouter layer or surface of a reducible polymer. Associated with saidphotosensitive elementis a rupturable container 56 carrying a liquidprocessing composition, which composition includes at least a solventfor said color-providing substance. The imagewise distribution ofunexhausted developing agent formed during processing reduces thereducible polymer present, in the form of particles, in the unexposedareas of the emulsion. Such reduction renders the particles permeable tothe processing composition which solubilizes the color-providingsubstance contained in such reduced particles. The solubilizedcolor-providing substance is transferred to the image-receiving layer toprovide the desired positive image; 7

While the silver halide developing agent maybe initially present in theliquid processing composition or in the photosensitive element, it isalso within'the scope of this invention to dispose a portion of thetotal silver halide developing agent in the liquid processingcomposition and a portion in the photosensitive element. Such an embodiment would facilitate the formation of a uniform dis- Development of thesilver halide imagewise distribution of tribution of the silver halidedeveloping agent in the photosensitive emulsion layer duringdevelopment.

' This invention has been illustrated with reference to processes forthe formation of positive c'olor transfer images, wherein acolor-providing substance is transferred to the'image-receiving element.It is also contemplated to initially dispose a color-providing substancein the image-receiving element and cause it to be removed from saidelement by the action of unexhausted developing agent on a reduciblepolymer controlling such color-pro-' viding substance. In such anembodiment, one may obtain a negative image.

In lieu of releasing a color-providing ciated with theimage-receivingelement, a visible image may be created as a result of achange in color of the portions of the reducible polymer reduced byunexhausted developer, followed by stabilization of the polymer layer.Thus a polymeric coupler which has been coupled to give, for example, anindophenol dye, will be rendered colorless in reduced areas. The polymermay be stabilized in its reduced and unreduced forms by an acidictreatment, such for example, as with boric acid. 'A positive image maybe obtained by using a white or colorless reducible polymer, e.g., apolymer containing triazoliurn groups, the reduced portions of whichwill be colored.

, FIG. 4 is illustrative of the last-mentioned embodiment and shows aphotographic product wherein a support layer 70 carries a photosensitivelayer 72. Associated therewith is a rupturable container 74 holding aprocessing composition and an image-carrying element comprising asupport 78 carrying a layer 76 of a reducible polymer.

substance asso- V Rupture of the container 74 releases the processingcomposition which permeates the photosensitive emulsion layer 72 andinitiates development thereof. As the latent image is developed, animagewise distribution of unexhausted developing agent is transferred tothe layer 76 of reducible polymer. Where the reducible polymer isinitially colored, e.g., an indophenol polymer, the reduced portionsmaybe rendered colorless to give a negative image. Where the reduciblepolymer is initially colorless or white, the reduced areas may berendered colored to give a positive image. I f

As indicated above, it is within the scope ofthis invention to utilizecolor-providing substances which are oxidized after. transfer to theimage-receiving material. An example of such a color-providing substanceis an indophenol dye, which is transferred in the reduced or leucostate, wherein it is colorless or less colored, and which must beoxidized to give the desired color. Such oxidation may be effected byaerial oxidation or by the use of suitable oxidizing agents which may beincorporated in the image-receiving element or applied thereto afterseparating apart from the photosensitive element.

The incorporation of an oxidizing agentin the imagereceiving element isdescribed in US. Patent No. 2,559,643, issued to Edwin H. Land. Asexamples of suitable oxidizin agents, mention may be made of peroxycompounds such as sodium or potassium perborate, and compounds havingpolyvalent metallic elements in higher valent form, such as copper, ironor cerium, wherein the metallic element is in higher valent form.Examples of these'latter-mentioned agents are cupric salts such ascupric sulfate. 'Another suitable oxidizing agent is benzoyl peroxide.Other suitable oxidizing agents include quinones, such as benzoquinone.A preferred quinone is 2,3-dicyanobenzoquinone, since the correspondinghydroquinone is too weak a reducing agent to interfere in development ofthe latent image.

The following examples are intended to illustrate methods by which anegative transfer image may be ob taincd using a reducible polymericmaterial, and are not intended to be interpreted in a limiting sense.

Example 1 A photosensitive element similar to that illustrated in FIG. 4is prepared by coating 3. subcoated cellulose acetate film base with asilver halide emulsion. An image-carrying element is prepared by coatinga cellulose acetatecoated baryta paper with a composition comprising 4%Nylon Type F8 (trade name of E. I. du Pont de Nemours & Co., Wilmington,Delaware, for N-methoxymethyl polyhexamethylene adiparnide) in 80%aqueous isopropanol. After this coating has dried, a coating ofpolyvinyl salicylal is applied using a 4% solution of polyvinylsalicylal in acetone. The polyvinyl salicylal is coupled by treatmentwith 0.5% of 2-amino-5-diethylaminotoluene in 1% sodium hydroxidefollowed by treating with aqueous ferricyanide. After rinsing twice withwater, the imagecarrying element is ready for use. The photosensitiveelement is exposed and an aqueous liquid processing compositioncomprising:

Percent Sodium carboxymethyl cellulose 4.5 Sodium hydroxide 2.0Potassium bromide 0.5 Sodium sulfite 0.5 Toluhydroquinone 0.5

is applied by spreading between said photosensitive element and saidimage-carrying element, as said elements are brought into superposedrelationship. After an imbibition period of approximately two minutes,the imagecarrying element is stripped apart to reveal a cyan negativeimage and is swabbed with 2% boric acid.

Example 2 An image-carrying element similar to that used in Example l isprepared by treating the layer of polyvinyl salicylal with a solution of0.5% of N,2,6-trichloro-pquinoneimine in 1% sodium hydroxide to effectcoupling, after which the image-carrying element is rinsed with water.After exposure, a photosensitive element is processed by the applicationof an aqueous liquid processing composition comprising:

Percent Sodium carboxymethyl cellulose 4.5 Sodium hydroxide 2.0Potassium bromide 0.5 Sodium sulfitel 2.0 Toluhydroquinone 0.5

spread between the exposed photosensitive element and the image-carryingelement as said elements are brought into superposed relationship. Thestripped image-carrying element has a cyan negative image and is swabbedwith 2% boric acid. A

The following example illustrates the embodiment described in connectionwith FIG. 2 using a colored reducible polymer.

Example 3 A photosensitive element is exposed and then developed with anaqueous liquid processing composition comprising:

Percent Sodium earboxymethyl cellulose 4.5 Sodium hydroxide g 2.0Potassium bromide 0.5 Sodium sulfite 0.5 Toluhydroquinone 0.5 Azorubine(Cl. 179) 2.0

solubility in the reducible solvent or plasticizer than in alkali, untilsaid solvent is reduced. Upon reduction of at least a portion of thereducible solvent comprising the particle, the color-providing substanceis rendered diffusible. Suitable reducible solvents may comprisemixtures of quinones or indophenols, with a small proportion of an inertmaterial, such as a high boiling, alkali-immiscible liquid, if necessaryto keep such solvent in liquid form.

In all products employed in the practice of this invention, it ispreferable to expose the photosensitive element from the emulsion side.It is, therefore, desirable to hold said photosensitive element and theimage-receiving element together at one end thereof by fastening meansnot shown but comprising hinges, staples, or the like in such mannerthat the photosensitive element and the image-receiving element may bespread apart from their processing positions illustrated in FIG. 1.Where the film unit is of the roll film type, said photosensitiveelement and image-receiving element are wound into separate rolls andthe free ends of said rolls are connected together in the mannerdescribed. A camera apparatus suitable for processing roll film of thetype just mentioned is providde by the Polaroid Land Camera Model A,sold by Polaroid Corporation, Cambridge, Massachusetts, or similarcamera structure such, for example, as the camera forming the subjectmatter of US. Patent No. 2,435,717. Camera apparatus of this typepermits successive exposure of individual frames of the photosensitiveelement from the emulsion side thereof as well as individual processingof an exposed frame by bringing said exposed frame into superposedrelation with a predetermined portion of the image-receiving elementwhile drawing these portions of the film assembly between a pair ofpressure rollers which rupture a container associated therewith andeffect the spreading of the processing liquid released by rupture ofsaid container, between and in contact with the exposed photosensitiveframe and the predetermined, registered area of the image-receivingelement. I i

The nature and construction of rupturable containers, such as container18 of FIG. 1, is well understood in the art; see, for example, U.S.Patent No. 2,543,181, issued to Edwin H. Land on February 27, 1951, andUS. Patent No. 2,634,886, issued to Edwin H. Land on April 14, 1 953.

The liquid processing composition utilized to process the exposedphotosensitive element comprises at least an aqueous solution, and maycontain an alkaline reagent. It is a solvent for the color-providingsubstance employed. If the liquid processing composition is to beapplied to the exposed photosensitive element by being spread thereon,preferably in a relatively thin, uniform layer, it may also include aviscosity-increasing compound constituting a film-forming material ofthe type which, when said composition is spread and dried, will form arelatively firm and relatively stable film. A preferred film-formingmaterial is a high molecular weight polymer such as a polymericwater-soluble ether which is inert to an alkaline solution as, forexample, a hydroxyethyl cellulose or sodium carboxymethyl cellulose.Other film-forming materials or thickening agents, whose ability toincrease viscosity is substantially unaffected when left in solution fora long eriod of time, may also be used. The film-forming material ispreferably contained in the processing composition in suitablequantities to impart to said composition a viscosity in excess of 1,000centipoises at a temperature of approximately 24 C. and preferably ofthe order of 1,000 to 200,000 centipoises at said temperature.Illustrations of suitable liquid processing compositions may be found inthe several patents and copending applications herein mentioned, andalso in the examples herein given. Under certain circumstances, it maybe desirable to apply the liquid processing composition to thephotosensitive element prior to exposurein accordance with the techl 1nique described in the copending application of Edwin H. Land, SerialNo. 498,672, filed April 1, 1955.

The image-receiving or image-carrying element comprises animage-receiving layer of opaque or transparent material which is liquidpermeable and dyeable from allealine solutions and which has beenillustrated for purposes of simplicity as comprising a single sheet ofpermeable material, for example paper. This element, how ever, maycomprise a support upon which at least one liquid-permeable and dyeablelayer is mounted, in certain instances, it may also carry a layer of areducible polymer, and such layer may also constitute the imagecarryinglayer. The support layer may have a water-impermeable subcoat over whichthe stratum of permeable anddyeable material is applied. In certaininstances, the dyeable layer; may comprise a layer of liquid processingcomposition which is adapted to remain adhered to the support layer uponstripping.

A preferred material for the'image-receiving layer is a nylon andpreferably a nylon such as N-methoxymethyl polyhexamethylene adipamidewhich is available under the trade name of Nylon Type F8 from E. I. duPont de Nemours & Co. Other materials suitable for image-receivinglayers comprise a partially hydrolyzed polyvinyl acetate such as thatcommercially available under the trade name of Vinylite MA-28-18 fromBakelite Division,

Carbide and Carbon Chemicals Co.; polyvinyl alcohol with or withoutplasticizers; baryta paper, i.e., a support having a baryta coatingthereon; cellulose acetate with filler as, for example, one-halfcellulose acetate and onehalf oleic acid, and other materials of asimilar nature, as is well known in the art.

While a rupturable container 18, such as has been illustrated with thefilm unit of FIG. 1, provides a convenient means for spreading a liquidprocessing composition between layers of a film unit whereby to permitthe processing to be carried out within a camera apparatus, the practiceof this invention may be otherwise efiected. For example, aphotosensitive element, after exposure in suitable apparatus and whilepreventing ftuther exposure thereafter'to actinic light, may be removedfrom such apparatus and permeated with the liquid processing compositionas by coating the composition on said photosensitive element 'orotherwise wetting said element with the composition following which thepermeated, exposed, photosensitive element, still without additionalexposure to actinic light, is brought into contact with theimage-receiving element for image formation in the manner heretoforedescribed.

It is also to be understood that the invention may be successfullypracticed without the use of a film-forming material in the liquidprocessing composition. As an illustration, a. nonviscous. liquidprocessing composition is particularly applicable with the processingtechnique last mentioned above and may be applied to the exposedphotosensitive element by imbibition or coating practices and may besimilarly applied to the image-receiving element before said elementsare brought into superposed relation or contact for carrying out thetransfer of mobile, diffusible color-providing substances.

It is recognized that it has been previously proposed in U.S. Patents.Nos. 2,661,293, issued December 1, 1953,

and 2,698,244, issued December 28, 1954, both in the name of Edwin H.Land, to form a positive image by action of unexhausted developerdiiiused from unexposed areas of a photosensitive element to asuperposed imagereceiving element containing a reducible metallic salt,the diffused, unexhausted developer reducing the metallic salt to give apositive image in terms of a metallic pigment. The invention herein setforth is readily distinguished from the above-mentioned disclosure sinceit is herein contemplated that the unexhausted developer be utilized toreact with a reducible organic material, and preferably a reduciblepolymer.

The processes of this invention may be similarly distinguished fromprior proposals to utilize unexhausted silver halide developing agent inthe formation of a positive transfer color image, such, for example, asthe aforementioned U.S. Patent No. 2,661,293. The processes contemplatedin said patent involve the transfer of unexhausted silver halidedeveloping agent to the imagereceiving material where it enters into acoupling or dyeforming reaction.

The processes of this invention may be similarly distinguished from theinvention disclosed and claimed in my copending application Serial No.599,122, filed July 20, 1956,. now abandoned in favor of acontinuation-inpart thereof, Serial No. 825,359, filed July 6, 1959. Theprocesses of that invention utilize unexhausted developing agent to actupon a reducible color-providing substance, the reduced form of which istransferable, as distinguished from the nontransferable reduciblesubstances of this invention.

While this invention has been illustrated by the formation ofmonochromatic color images, it is to be understood that it may beutilized in the formation of multicolor images. In such embodiments, theuse of reducible polymeric materials may beemployed to provide one ormore of the requisite monochromatic images. The techniques of thisinvention are particularly useful in multicolor processes since theypermit the use of colorproviding substances which are photographicallyunreactive. By way of. illustration, reducible polymeric materials suchas contemplated herein may be employed in the multilayer delayedtransfer processes disclosed and claimed in the copending application ofEdwin H. Land and Howard G. Rogers, Serial No. 565,135, filed February13, 1956, as, for example, to control a color-providing substanceassociated with the innermost emulsion. In such a multilayer embodiment,it may be desirable to utilize a developing agent having relatively lowmobility or diffusibility to restrict the developing agent to itsparticular environment and associated reducible polymeric material. Useof such low mobility developing agents may avoid or reduce any need forany other barrier layer, such as disclosed in the said copendingapplication,

' Serial No. 565,135.

The inventive concepts herein set forth are also adaptable for theformation of multicolored images in accordance with the photographic.products and processes of the aforementioned U.S. Patent No. 2,647,049.

Similarly, the inventive concepts herein disclosed are adaptable for usein photosensitive screen products and processes wherein thephotosensitive screen elements are prepared as disclosed in the saidcopending application of Howard G. Rogers, Serial No. 415,073, nowabandoned, and also in the copending application of Edwin H. Land,Serial No. 448,441, filed August 9, 1954, now U.S. Patent No. 2,968,554.

Although the concepts of this invention have been illustrated inone-step, diffusion-transfer processes and possess unique advantages insuch processes, it is contemplated that in certain instances theseconcepts also may be employed in multiple-step processes In such cases,the emulsion medium should be one which is rendered more insoluble orimpermeable by the action of the developing agent used to developexposed areas, as by tanning, and is substantially unaffected byunexhausted developing agent in unexposed areas. After development iscompleted, a stronger developer or other reducing agent may be employedto reducethe reducible polymeric material. In the exposed areas, thestronger eveloping agent cannot permeate through the emulsion to reducethe reducible polymer, while in unexposed areas, it is capable ofreaching and reducing the reducible polymer to release thecolor-providing substance for transfer.

Throughout the specification and appended claims, the expressionpositive image has been used. This expres sion should not be interpretedin a. restrictive sense since it is used primarily for purposes ofillustration, in that it defines the image produced on theimage-carrying layer as being reversed, in the positive-negative sense,with respect to the developed image in the photosensitive element. As anexample of an alternative meaning for positive image, assume that thephotosensitive element is exposed to actinic light through a negativetransparency. In this case, the latent image in the photosensitiveelement will be a positive and the image produced on the image-carryinglayer will be a negative. The expression positive image is intended tocover such an image produced on the image-carrying layer. It is to beunderstood that certain embodiments of this invention may be used toobtain negative transfer images of the developed image, as hereinbeforeset forth.

In preceding portions of the specification, the expression color hasbeen frequently used. This expression is intended to include the use ofone or more colors to obtain black.

Throughout the specification and claims, the expression super-posing hasbeen used. This expression is intended to cover the arrangement of twolayers in overlying relation to each other either in face-to-facecontact or in separated condition and including between them at leastone layer or stratum of a material which may be a viscous liquid.

Since certain changes may be made in the above products and processesWithout departing from the scope of the invention herein involved, it isintended that all matter contained in the above description or shown inthe accompanying drawing shall be interpreted as illustrative and not ina limiting sense.

What is claimed is:

1. The process comprising developing an exposed silver halide emulsionwith an aqueous alkaline solution containing a silver halide developingagent, said silver halide developing agent being present in suchquantity per unit area of silver halide emulsion as to be substantiallycompletely reacted in fully developed areas of said emulsion, forming inundeveloped areas of said emulsion as a result of said development animagewise distribution of unoxidized silver halide developing agenthaving a concentration substantially inversely proportional to thedegree of development per unit area of said silver halide emulsion,reducing a reducible polymer imagewise with said unoxidized silverhalide developing agent, said reducible polymer being the productobtained by coupling the oxidation product of a color developer with apolyvinyl acetal formed from polyvinyl alcohol and an aromatic aldehydeselected from the group consisting of aromatic aldehydes containingbenzene and naphthalene nuclei containing a hydroxyl group and having anavailable coupling position para to said hydroxyl group, the substituentformed by said coupling reaction being reducible by said unoxidizedsilver halide developing agent less readily than is said exposed silverhalide but more readily than is said unexposed silver halide, saidreduction of said substituent of said reducible polymer forming theleuco derivative of said substituent.

2. A process as defined in claim 1, wherein said substituent of saidreducible polymer is colored, said leuco derivative is substantiallycolorless, the layer containing said reducible polymer is separated fromsuperposition with said exposed silver halide emulsion after said leucoderivative has been formed, and said separated layer containing saidreducible polymer treated with an acidic solution to stabilize thereduced and unreduced forms of said reducible polymer, thereby providinga negative transfer image in said polymer layer of the developed areasof said exposed silver halide emulsion.

3. A process as defined in claim 1, wherein said reducible polymer isthe cyan coupling product of polyvinylsalicylal and the oxidationproduct of 2-amino-5- diethylaminotoluene, and said silver halidedeveloping agent is toluhydroquinone.

4. A process as defined in claim 1, wherein said reducible polymer isthe cyan coupling product of polyvinylsalicylal andN,2,6-trichloro-p-quinoneimine, and said silver halide developing agentis toluhydroquinone.

5. A process as defined in claim 1, wherein the portions of saidreducible polymer unreduced by said silver halide developing agent aresubstantially impermeable to said aqueous alkaline solution, andportions of said reducible polymer which are reduced by said unoxidizedsilver halide developer are permeable to said aqueous alkaline solution,and a dye is difiused into and through said reduced, permeable portionsof said reducible polymer to form a positive image of the developedareas of said exposed silver halide emulsion.

References Cited in the file of this patent UNITED STATES PATENTS2,538,257 Martin Jan. 16, 1951 2,614,926 Land Oct. 21, 1952 2,647,049Land July 28, 1953 2,661,293 Land Dec. 1, 1953 2,698,798 Land Jan. 4,1955 2,704,711 Hanson Mar. 2 1955 2,774,668 Rogers Dec. 18, 1956

1. THE PROCESS COMPRISING DEVELOPING AN EXPOSED SILVER HALIDE EMULSIONWITH AN AQUEOUS ALKALINE SOLUTION CONTAINING A SILVER HALIDE DEVELOPINGAGENT, SAID SILVER HALIDE DEVELOPING AGENT BEING PRESENT IN SUCHQUANTITY PER UNIT AREA OF SILVER HALIDE EMULSION AS TO BE SUBSTANTIALLYCOMPLETELY REACTED IN FULLY DEVELOPED AREAS OF SAID EMULSION, FORMING INDEVELOPED AREAS OF SAID EMULSION AS A RESULT OF SAID DEVELOPMENT ANIMAGEWISE DISTRIBUTION OF UNOXIDIZED SILVER HALIDE DEVELOPING AGENTHAVING A CONCENTRATION SUBSTANTIALLY INVERSELY PROPORTIONAL TO THEDEGREE OF DEVELOPMENT PER UNIT AREA OF SAID SILVER HALIDE EMULSION,REDUCING A REDUCIBLE POLYMER IMAGEWISE WITH SAID UNOXIDIZED SILVERHALIDE DEVELOPING AGENT, SAID REDUCIBLE POLYMER BEING THE PRODUCTOBTAINED BY COUPLING THE OXIDATION PRODUCT OF A COLOR DEVELOPER WITH APOLYVINYL ACETAL FORMED FROM POLYVINYL ALCOHOL AND AN AROMATIC ALDEHYDESELECTED FROM THE GROUP CONSISTING OF AROMATIC ALDEHYDES CONTAININGBENZENE AND NAPHTHALENE NUCLEI CONTAINING A HYDROXYL GROUP AND HAVING ANAVAILABLE COUPLING POSITION PARA TO SAID HYDROXYL GROUP, THE SUBSTITUENTFORMED BY SAID COUPLING REACTION BEING REDUCIBLE BY SAID UNOXIDIZEDSILVER HALIDE DEVELOPING AGENT LESS READILY THAN IS SAID EXPOSED SILVERHALIDE BUT MORE READILY THAN IS SAID UNEXPOSED SILVER HALIDE, SAIDREDUCTION OF SAID SUBSTITUENT OF SAID REDUCIBLE POLYMER FORMING THELWUCO DERIVATIVE OF SAID SUBSTITUENT.
 2. A PROCESS AS DEFINED IN CLAIM1, WHEREIN SAID SUBSTITUENT OF SAID REDUCIBLE POLYMER IS COLORED, SAIDLEUCO DERIVATIVE IS SUBSTANTIALLY COLORELESS, THE LAYER CONTAINING SAIDREDUCIBLE POLYMER IS SEPARATED FROM SUPERPOSITION WITH SAID EXPOSEDSILVER HALIDE CMULSION AFTER SAID LEUCO DERIVATIVE HAS BEEN FORMED, ANDSAID SEPARATED LAYER CONTAINING SAID REDUCIBLE POLYMER TREATED WITH ANACIDIC SOLUTION TO STABILIZE THE REDUCED AND UNREDUCED FORMS OF SAIDREDUCIBLE POLYMER, THEREBY PROVIDING A NEGATIVE TRANSFER IMAGE IN SAIDPOLYMER LAYER OF THE DEVELOPED AREAS OF SAID EXPOSED SILVER HALIDEEMULSION.